The time required for perceptual (nonmotoric) processing in IOR.

In an inhibition of return (IOR) paradigm, we used a threshold-tracking procedure combined with backward masking to measure the speed of perceptual processing in IOR independent of motoric factors. Instead of the conventional reaction time measure, this procedure yielded the critical exposure duration (DURc) that is required in order for a target to be identified reliably before the onset of a trailing mask. In Experiment 1, the facilitation effects conventionally found at short cue-target onset asynchrony (CTOA) were evidenced by shorter values of DURc at cued relative to uncued locations. Conversely, the retardation effects conventionally found at long CTOA were evidenced by correspondingly longer values of DURc. In Experiment 2, the DURc results strongly suggest that the directional reading bias previously observed in IOR studies is due, at least in part, to perceptual rather than motoric factors.